1. Field of the Invention
The present invention relates to 1,3-dialkyl-2-imidazolidinone and a preparation process of the same. More specifically, the invention relates to high-purity 1,3-dialkyl-2-imidazolidinone which can be obtained by reacting N,N'-dialkylethylenediamine with urea and has a very low content of a by-product, and a process for preparing the same.
1,3-Dialkyl-2-imidazolidinone is an aprotic solvent having high polarity, is very stable to acid and alkali compared with a conventional aprotic polar solvent, and has high dissolving power for various inorganic and organic compounds.
Thus, 1,3-dialkyl-2-imidazolidinone is a very useful compound as a solvent for preparing medicines, agricultural chemicals, dyestuffs and pigments, an agent for cleaning electronic parts and molds, and a solvent for polymerizing high polymer compounds.
2. Related Art of the Invention
1,3-Dialkyl-2-imidazolidinone has been conventionally prepared by a known process which reacts N,N'-dialkylethylenediamine with urea. The process was simple and excellent, but had a disadvantage of low yield. Later developments have improved the disadvantage.
U.S. Pat. No. 4,731,453 has disclosed a process for preparing 1,3-dialkyl-2-imidazolidinone in the yield of 80% or more by heating N,N'-dialkylethylenediamine and urea at temperature of 180.degree. C. or more, preferably by previously completing the forming reaction of 1,1'-dimethyl-1,1'-dimethylenebisurea intermediate at 140.degree. C. and successively reacting at temperature of 180.degree. C. or more. However, according to the process, the product contains a by-product 1,3-dimethyl-2-imidazolidinimine in an amount of 0.5 to a few percents for 1,3-dimethyl-2-imidazolidinone. The by-product has a boiling point which is close to the boiling point of 1,3-dimethyl-2-imidazolidinone, and thus requires a column having a very high theoretical plate number in order to separate by distillation or a process for carrying out alternative treatment. Thus, the process of the U.S. Patent has problems in view of by-product removal.
When 1,3-dimethyl-2-imidazolidinone containing the by-product as above is used as a solvent, the by-product inhibits the desired reaction. For example, in the case of using as a solvent for preparing aramid, the by-product inhibits polymerization of the polymer.
Thus, 1,3-dimethyl-2-imidazolidinone has disadvantages in practical application.
However, the direct preparation process of 1,3-dialkyl-2-imidazolidinone from N,N'-dialkylethylenediamine and urea has merits of 1 low material cost and 2 no requirement for separating formed water as compared with conventionally known processes and is thus excellent as a process for manufacturing 1,3-dialkyl-2-imidazolidinone in an industrial scale. Consequently, the direct preparation process of 1,3-dialkyl-2-imidazolidinone in the absence of by-product formation has been strongly desired.